a = input("请输入英文文本：")
# 初始化字典
n = {}
for char in a:
    char = char.lower()
    if char.isalpha():
        n[char] = n.get(char, 0) + 1

p = sorted(n.items())

print("\n字母频率统计：")
for char, count in p:
    print(f"{char}: {count}")